Conventional video scan formats are generally categorized into a progressive-scan type and an interlaced-scan type. The video scan format governs the mode of transmission of a video. A software player or a hardware player decodes and plays the video according to header data of the video, and especially header data concerning the scan format.
For example, a conventional TV screen, e.g. a cathode ray tube (CRT) screen, generally adopts an interlaced-scan type of video scan format. The interlaced-scan process scans the lines of a video from top to bottom, e.g. scanning the odd-numbered scan lines (1, 3, 5 . . . ) and the even-numbered scan lines (2, 4, 6 . . . ) in an interlaced manner. The odd-numbered scan lines form a kind of field, namely a top field. The even-numbered scan lines form another kind of field, namely a bottom field. The scan lines of the top field and the scan lines of the bottom field are interlaced to form a frame. With the interlaced scan type, one field is composed of either the odd-numbered scan lines or the even-numbered scan lines, and only half of the scan lines will be transmitted and displayed at a time. However, the human eye will not notice that only half of the scan lines are displayed, but will perceive a full frame due to persistence of vision.
Unlike the interlaced-scan video, each frame of a progressive-scan video can be obtained by scanning the scan lines of a video one-by-one in a consecutive order. The progressive-scan video is a full-frame based video without the aspect of the fields.
However, if the header of the video records a wrong video scan type, the player may not play the video correctly, such that unstable video images may be produced thereby. In an exemplary example, the player is such as a television. The player extracts data from a video header when it receives a video to determine the scan type thereof, i.e., a progressive-scan video or an interlaced-scan video, then plays the video by an appropriate scan algorithm. For example, when the player, e.g. a television, receives an interlaced-scan video from a television station, the television plays the video by performing a de-interlaced scan algorithm for gaining an optimal visual effect. Otherwise, a zipper phenomenon may occur if the television plays the interlaced-scan video by a progressive-scan process. Furthermore, image flickering, e.g., overlapping or zigzagging at the edges of the video, may occur if a TV program is played in a wrong scan type on a media player of a computer.